One form of conventional sport or work knives comprises a handle and one or more folding blades. The blades in such knives are closed simply by pressing on the back of the blade and rotating the blade to a closed position in the knife handle. Such knives are known for their ability to close when being used if a pressure is inadvertently applied to the back of the blade.
To protect against inadvertent closure, locks were developed for locking a blade in an open position. A common type of locking element known as a liner lock extends longitudinally through the handle and is spring biased to snap into position adjacent to the hinged end (tang) of the blade when the blade is opened. As long as the locking element is retained in the locked position behind the blade, the locking element prevents the blade from pivoting to the closed position. A projecting portion of the locking element or other release mechanism is manipulated to manually move the locking element laterally away from the blade swing path so that the blade can be closed.
Folding knives having such liner locks have become common. However, because the lock feature is defeated by manipulation of an element on the knife handle, the lock can be defeated inadvertently during use of the knife if sufficient pressure is applied to the flexible locking element. To protect against inadvertent movement of the locking element, U.S. Pat. No. 5,596,808 discloses a safety mechanism that is manually movable to a safety position in which the mechanism interferes with the movement of the locking element to its unlocked position. To close the blade, the safety mechanism is first moved to a release position, which then allows the locking element to be moved to its unlocked position so that the blade can be closed.
While the device of the '808 patent is an improvement to the conventional liner lock, there is a continuing need for new and improved devices for folding knives that protect against the inadvertent closure of the knife blade.